NCERT Solutions for Class 7 Science Chapter 14 Electric Current and its Effects are part of NCERT Solutions for Class 7 Science. Here we have given NCERT Solutions for Class 7 Science Chapter 14 Electric Current and its Effects.
|Chapter Name||Electric Current and its Effects|
|Number of Questions Solved||13|
NCERT Solutions for Class 7 Science Chapter 14 Electric Current and its Effects
Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position and battery.
Draw the circuit diagram to represent the circuit shown in Fig.
The bulb in the circuit shown in Fig. does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
The problem in this circuit is the connection of two cells. Here both the positive terminals of the cells are connected to each other. This must be reversed for any one cell to make the bulb glow i.e., positive terminal of one cell should be connected with the negative terminal of the other.
Name any two effects of electric current.
(i) Heating effect.
(ii) Magnetic effect.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
We know that the needle of a compass is itself a tiny magnet, which points in north-south direction. When we bring a magnet close to it, the needle gets deflected. When electric current passes through a wire it also behaves like a magnet. And hence the needle of the compass will also be deflected.
Will the compass needle show deflection when the switch in the circuit shown by Fig. is closed?
No. Because there is no cell/battery in the circuit and hence no current will flow through the wires.
Fill in the blanks:
(a) Longer line in the symbol for a cell represents its …….. terminal.
(b) The combination of two or more cells is called a ……… .
(c) When current is switched ‘on’ in a room heater, it …….. .
(d) The safety device based on the heating effect of electric current is called a ….. .
(a) positive battery
(c) becomes red hot
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)
(b) When the electric current, through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)
(c) An electromagnet does not attract a piece of iron. (T/F)
(d) An electric bell has an electromagnet. (T/F)
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
No. An electromagnet develops magnetic property and it will attract only the magnetic substances. Since the plastic bags are non-magnetic so they cannot be separated from a garbage heap by an electromagnet.
An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.
No, I will not agree. Electric fuse is made from some special material which blows off when the current exceeds the safe limit, while an ordinary wire may not perform this function and will cause damages to electrical circuits and appliances and also can cause fires. Hence I will insist to use proper fuse wire carrying ISI mark.
Zubeda made an electric circuit using a cell holder shown in the following Fig., a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
These may be the reasons by which bulb will not glow.
(i) The cell may be connected in improper way. Check out that the positive terminal of one cell is connected to the negative terminal of the other or not.
(ii) The junctions of the wire may be loose. Check them again.
(iii) Check the condition of the bulb. Replace it. if it is fused.
In the circuit shown in the following Fig.:
(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?
(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?
(i) No. None of the bulbs will glow unless the switch is in the ‘ON’ position.
(ii) All the three bulbs will glow at the same time as far as the capacity of the battery is concerned.
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